Molybdenum films deposited on Si3N4 ceramics have been given an N+ ion beam mixing (IBM) treatment with an energy of 120 keV and doses of 2 x 10(15), 1 x 10(16) and 5 x 10(16) ions cm(-2). The IBM modified surfaces were investigated by X-ray photoelectron spectroscopy, Auger electron spectroscopy and X-ray diffraction. The scratch tests show that N implantation increased adhesion of film to ceramics significantly. The reciprocating friction tests show that IBM modified Si3N4 exhibited friction reduction under no lubrication. The good adhesion strength can be attributed to the formation of an Mo-C compound in the Mo-Si3N4 interface, Mo-N solid solution in the molybdenum films, and recoil implantation of molybdenum into ceramics.